Large amounts of macro-and micro-plastic have been reported in rivers, lakes and oceans. However, links between the observed pollution and their sources remain unclear. This study aims to clarify these links in the Lake Geneva basin by analysing each step of the watershed's plastic life cycle.Two distinct approaches are compared: (i) a top-down approach based on modelling socio-economic activities, plastic losses and releases into the lake, and, (ii) a bottomup approach based on the extrapolation of plastic flows into the lake from field measurements across 6 different pathways.The two approaches yield results with similar orders of magnitude: 49 tons.year -1 (range 8-193 tons.year -1 ) for the top-down approach, and 59 tons.year -1 (range 34-83 tons.year -1 ) for the bottom-up approach. From this, we estimate plastic flows from land to Lake Geneva -approximately 55 tons.year -1 .Field measurements (bottom-up) showed significant contribution of water run-off as a pathway for plastics, mainly through rivers in wet periods and road-runoff. The samples analysed contained mainly plastic waste from packaging and plastic from the construction industry. The modelling approach (top-down) indicated that abrasion of car tyres could be a major contributor to plastic pollution (one order of magnitude higher than all other sources), as well as textile fibres to a lesser extent. As these particles have not been traced in the environment, further studies are needed to validate these theoretical findings.Preliminary mass balance of plastic in Lake Geneva indicates that 20% of plastic may be deposited on shores, 10% flows in the emissary towards the sea and the rest being deposited in the sediments. We take from these findings that Lake Geneva acts as a sink for plastic pollution, with close to 600 tons accumulation of plastic in lake sediments (i.e. 3 order of magnitude more than the expected surface floating plastic). These findings bring a novel insight into the role of big and deep lakes as a filter for plastic (no flushing through flooding period), thus preventing more plastic from reaching the oceans. This research allows for the first time the combination of bottom-up and top-down modelling approaches as well as plastic stock assessment. In spite of the high uncertainties embedded in such approaches, and the fact that contemporary methods are not suitable for the detection of very small particles or particles maintaining certain characteristics, it provides a comprehensive model of plastic leakage into waterways. We believe such approaches should be replicated in other areas by refining the analytical approaches.

Abstract:The research investigates the role the environmental manager plays to ensure a successful (or not) implementation of environmental performance within an organization. It is based on interviews of 5-7 actors per company within a sample of 7 companies (42 interviews). We build upon bias of perception of the various actors interviewed within each company to define 4 paradoxes related to the roles and mission of the environmental manager that hinder proper efficiency of environmental management at company level. Paradox 1 is that no one takes ownership of environmental performance within the organization. Paradox 2 is that the environmental manager is in an awkward situation vis-à-vis his boss. Paradox 3 is that the role of the environmental manager in relation to employees is ambiguous. Paradox 4 is that corporate and product approaches are decoupled. We suggest that these paradoxes interact and form a vicious cycle that may, in part, be responsible for the environmental decoupling phenomenon-companies often adopt a sustainability policy symbolically without implementing it substantively. Our research suggests that, by leveraging the leadership of the environmental manager through organizational and motivational measures, the vicious cycle can be transformed into a virtuous cycle and the human motivation can become a driver for green change within corporations. We proposed the SEA (Shaping Environmental Action) model based of 4 pillars: information, motivation, organization, and strategy.

Abstract:The research investigates the role the environmental manager plays to ensure a successful 9 (or not) implementation of environmental performance within an organization. It is based on 10 interviews of 5-7 actors per company within a sample of 7 companies (42 interviews). 11We build upon bias of perception of the various actors interviewed within each company to define 18We suggest that these paradoxes interact and form a vicious cycle that may in part be responsible